CN107852201B

CN107852201B - Measurement procedure for DRS with beamforming

Info

Publication number: CN107852201B
Application number: CN201680041390.4A
Authority: CN
Inventors: M.弗伦内; R.M.哈里森; M.卡兹米
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2015-05-14
Filing date: 2016-05-11
Publication date: 2021-10-29
Anticipated expiration: 2036-05-11
Also published as: US20230216548A1; US10469138B2; US20180091196A1; EP3295581B1; CN114125872A; CN107852201A; US20200028546A1; US20210376885A1; US10917142B2; US11552679B2; EP3295581A1; WO2016181332A1

Abstract

Systems and methods relating to transmission and use of Discovery Reference Signal (DRS) signals are disclosed herein. In some embodiments, a method of operation of a Transmission Point (TP) in a cellular communications network comprises: the same one or more DRS signals are transmitted from the TP using at least two different transmission beams in at least two different time resources. Each transmit beam is characterized by the direction in which it is transmitted. In this way, TPs are enabled to reuse DRS resources, which in turn enables transmission of DRS signals on a larger number of transmission beams, and correspondingly enables adaptation of measurement procedures at the wireless apparatus to obtain measurements on those transmission beams.

Description

Measurement procedure for DRS with beamforming

RELATED APPLICATIONS

This application claims the benefit of provisional patent application serial No. 62/161,788 filed on 5,

month

5 and 14 of 2015, the disclosure of which is hereby incorporated by reference in its entirety.

Technical Field

This disclosure pertains to a measurement procedure for discovery signals employing beamforming.

Background

Long Term Evolution (LTE) frame structure and reference signals

Third generation partnership project (3 GPP) LTE technology is a mobile broadband wireless communication technology in which transmissions from a base station, referred to as an enhanced or evolved node b (enb), to a wireless device, such as a mobile station, referred to as a user equipment device (UE), are sent using Orthogonal Frequency Division Multiplexing (OFDM). OFDM splits a signal into multiple parallel subcarriers in frequency. As shown in fig. 1, the basic unit of transmission in LTE is a Resource Block (RB), which in its most common configuration consists of 12 subcarriers and 7 OFDM symbols (one slot). A unit of 1 subcarrier and 1 OFDM symbol is referred to as a Resource Element (RE). Thus, RB consists of 84 REs. An LTE radio subframe consists of two slots in time and a number of RBs in frequency, where the number of RBs determines the bandwidth of the system. Further, two RBs adjacent in time in a subframe are denoted as an RB pair. Fig. 2 shows RB pairs in a downlink subframe. Currently, LTE supports standard bandwidth sizes of 6, 15, 25, 50, 75 and 100 RB pairs.

In the time domain, LTE downlink transmissions are organized into 10 millisecond (ms) radio frames, each radio frame consisting of 10 equal-sized lengths T_Sub-frameSubframe configuration of =1 ms.

Discovery signals for small cells

With the densification of small cells (cells with lower transmit power and thus smaller coverage) and potentially an increase in the number of carriers in small cell scenarios, a Discovery Reference Signal (DRS) feature has been introduced in 3GPP LTE release 12 (Rel-12). In Rel-12, the DRS occasion has been defined as the duration within which the DRS signal is transmitted by the cell. The DRS signals contained in the DRS occasion on a cell are shown in fig. 3. Specifically, fig. 3 shows REs used by DRS signals (e.g., transmitted by two different Transmission Points (TPs)) in physical rb (prb) pairs of two different cells. As shown, the DRS signal contains a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a Common Reference Signal (CRS), and, if configured, a channel state information reference signal (CSI-RS). With respect to CSI-RS, fig. 3 shows both REs used for CSI-RS belonging to a DRS occasion and potentially REs used for CSI-RS belonging to a DRS occasion. Although the DRS signal enables small cell on/off, it can also be utilized when small cell on/off is not used in a cell and also in a non-small cell (with arbitrary transmit power).

The DRS signals in the DRS occasion consist of PSS, SSS, CRS, and (when configured) CSI-RS. PSS and SSS are used for coarse synchronization (when needed) and for cell identification. CRS is used for fine time and frequency estimation and tracking, and may also be used for cell validation, i.e., to confirm cell Identities (IDs) detected from PSS and SSS. CSI-RS is another signal that can be used in dense deployment of cells or TP identification. Fig. 3 shows the presence of these signals in a DRS occasion equal in length to two subframes, and also shows the signal transmission on two different cells or TPs.

The DRS occasion corresponding to transmission from a particular cell may range from 1 to 5 subframes for Frequency Division Duplex (FDD) and from 2 to 5 subframes for Time Division Duplex (TDD) in duration. The subframe where the SSS occurs marks the starting subframe of the DRS occasion. This subframe is either subframe 0 or subframe 5 in both FDD and TDD. In TDD, PSS occurs in subframe 1 and subframe 6, while in FDD, PSS and SSS occur in the same subframe. The CRS is transmitted in a special subframe downlink part (DwPTS) region of all downlink subframes and special subframes.

The CSI-RS may be transmitted in any downlink subframe, but with any constraints associated with each subframe. Because of the DRS signal, only a single port (port 15) of the CSI-RS is transmitted. There are up to 20 possible RE configurations within a subframe, although the number of configurations is constrained to 5 in subframe 0 (to account for transmission of a Physical Broadcast Channel (PBCH) using many of the same REs in 6 PRBs centered on the carrier frequency) and 16 in subframe 5. In a DRS occasion transmitted from a cell, CSI-RS intended to represent a single measurable entity (not strictly referred to as TP) can occur in any RE configuration in any downlink subframe that is part of the DRS occasion. Thus, considering that the DRS occasion may be up to 5 subframes long in the FDD frame structure, the maximum possible number of CSI-RS RE configurations is 96. This occurs when the DRS occasion starts at subframe 5 (the DRS occasion starting at subframe 0 will support fewer CSI-RS RE configurations) and consists of 16 configurations in

subframe

5 and 20 configurations in each of the four subsequent subframes.

It is possible for a cell or TP to transmit CSI-RS in some CSI-RS RE configurations, and nothing in other CSI-RS REs. The CSI-RE configurations in which some signals are transmitted are then indicated to the UE as non-zero power (NZP) CSI-RS RE configurations, while the CSI-RS configurations in which nothing is transmitted are indicated as Zero Power (ZP) CSI-RS RE configurations. With NZP and ZP CSI-RS RE configurations, CSI-RS from two different cells or TPs can effectively be orthogonal as shown in fig. 3.

In each CSI-RS RE configuration, the symbols transmitted in the RE may be scrambled with a sequence dependent on a virtual or configurable cell ID (vcid) that can assume the same set of values (i.e., up to 504 values) as the revision 8 cell ID. Although this creates the possibility of a very large number of CSI-RS possibilities, two CSI-RS transmitted with different scrambling codes on the same RE are not orthogonal. Therefore, it is less robust to separate different CSI-RS transmissions using only scrambling codes than using different RE configurations.

Radio Resource Management (RRM) measurements with DRS

A description of how RRM measurements are performed with DRS signals is now provided. DRS signals should be usable by UEs to perform cell identification, Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) measurements. The DRS signal based RSRP measurement definition is the same as that in the LTE previous releases. A Received Signal Strength Indication (RSSI) measurement is defined as the average over all OFDM symbols in the downlink portion of the measured subframe within a DRS occasion. RSRQ is then defined as:

DRSRQ=N x DRSRP/DRSSI，

where N is the number of PRBs used in performing the measurement, DRSRP is the DRS signal based RSRP measurement, and DRSSI is the RSSI measured on-the-fly at the DRS.

In Rel-12, CRS and CSI-RS based RSRP measurements in DRS occasions and CRS based RSRQ measurements in DRS occasions have been defined. As stated earlier, the DRS signal can be used in small cell deployments where the cell is switched off or on, or in general deployments where the on/off feature is not used. For instance, DRS signals can be used to make RSRP measurements on different CSI-RS configurations in the DRS occasion being used within a cell, which can enable detection of different TPs in a shared cell.

When measuring for CSI-RS in a DRS occasion, the UE constrains its measurements to a candidate list that is sent by the network to the UE via Radio Resource Control (RRC) signaling. Each candidate in this list contains the physical cell id (pci), VCID and subframe offset indicating the duration (in number of subframes) between the subframe in which the UE receives the CSI-RS and the subframe carrying the SSS. This information allows the UE to limit its search. The UE correlates to received signal candidates indicated by the RRC signal and reports back any CSI-RS RSRP values that have been found to meet a certain reporting criterion (e.g., exceed a threshold).

When a UE is being served on multiple carrier frequencies via a primary cell (PCell) and one or more secondary cells (scells), the UE needs to perform RRM measurements on other cells on the currently used carrier frequency (intra-frequency measurements) and on cells on other carrier frequencies (inter-frequency measurements). Since the discovery signal is not continuously transmitted, the UE needs to be informed about the timing of the discovery signal in order to manage its search complexity. Furthermore, when the UE is being served on as many carrier frequencies it can support and the inter-frequency RRM measurements need to be performed on different carrier frequencies not currently being used, the UE is assigned a measurement gap pattern. This gap pattern on the serving frequency allows the UE to retune its receiver from that serving frequency to another frequency on which measurements are being performed. During the duration of the measurement gap, the eNB cannot schedule the UE on the current serving frequency. Knowledge of the timing of the discovery signal is particularly important when such measurement gaps need to be used. In addition to mitigating UE complexity, this also ensures that the UE is not unavailable for scheduling for an extended period of time on the current serving frequency (PCell or SCell).

The provision of such timing information is done via a Discovery Measurement Timing Configuration (DMTC) signaled to the UE. DMTC provides a window of 6ms duration with some periodicity and timing occurrence within which a UE can expect to receive DRS signals. The duration of 6ms is the same as the measurement gap duration currently defined in LTE and allows the measurement procedures for DRS signals to be coordinated at the UE regardless of the need for measurement gaps. Only one DMTC is provided per carrier frequency (including the current serving frequency). The UE can expect that the network will transmit DRS signals such that all cells intended to be discoverable on the carrier frequency transmit DRS signals within a time window configured by the DMTC. Furthermore, when measurement gaps are needed, it is expected that the network will ensure sufficient overlap between the configured DMTC and the measurement gaps.

To ensure the operational efficiency of the network, it is important that the different groups of UEs being served by the eNB do not have the same measurement gap pattern defined for inter-frequency measurements, so that not all UEs are not available for simultaneous scheduling on the serving carrier frequency. Fig. 4 and 5 show some possible configurations of measurement gaps or DMTC time windows for a UE that meet the above constraints. In fig. 4, the measurement gap or DMTC periodicity is set to be a multiple of the DRS occasion periodicity. The UEs served by the eNB on the serving frequency are then divided into a plurality of non-overlapping groups. In fig. 4, the DRS occasion periodicity is 40ms, while the measurement gaps and DMTC are configured to occur every 80 ms. The UEs are divided into two groups so that when one group of UEs is performing inter-frequency measurements, the other group of UEs is available for scheduling. Fig. 5 shows an alternate configuration in which the DMTC time window and DRS occasion have the same periodicity. However, each cell transmits DRSs in multiple instances of a DRS occasion, and different groups of UEs are assigned different measurement gaps, or DMTCs, that are aligned with one of the instances of a DRS occasion.

Beamforming

To enhance system capacity and reduce interference, a network node (e.g., a base station or eNB) may use beamforming (i.e., UEs are served with transmit beams pointing in their direction). Beamforming is implemented by means of multiple-input multiple-output (MIMO) techniques, in which signals are transmitted in beams by applying the same signal to a plurality of co-located transmit antennas and applying a phase shift per transmit antenna. The phase shift determines the pointing direction of the transmit beam. MIMO indicates that both the network node and the UE employ multiple antennas, but it should be noted that transmit beamforming from the network node can also be used in case the UE has a single antenna.

The MIMO configuration is generally expressed by a notation (M × N) in terms of the number of transmit antennas (M) and the number of receive antennas (N). The prevalent MIMO configurations used are: (2 x 1), (1 x 2), (2 x 2), (4 x 2), (8 x 2), and (8 x 4). The MIMO configurations represented by (2 x 1) and (1 x 2) are special cases of MIMO, and they correspond to transmit diversity and receiver diversity, respectively. In LTE release 12 and release 13, up to M =16 and 32 are specified.

To create a large number of sharp beams in the vertical and azimuth directions, also known as three-dimensional beams, the network nodes may employ active antennas, also known as Active Antenna Systems (AAS). The AAS system includes an array of a large number of antenna elements in a specific arrangement. For example, they can be arranged in the form of a uniform linear array, a two-dimensional matrix (rows and columns), a ring, and the like. The antenna elements are electrically controlled to enable electronic amplification and/or other Radio Frequency (RF) processing. The electronic circuitry in the AAS system capable network node allows considerable flexibility to dynamically control beam characteristics such as direction, shape and strength of the beam. For example, the elevation and azimuth of the beam, the beamwidth of the radiation pattern, etc. can be electrically controlled, e.g., depending on the UE location.

Disclosure of Invention

In some embodiments, transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting the one or more DRS signals using the first transmission beam but not the second transmission beam in a first time resource, and transmitting the one or more DRS signals using the second transmission beam but not the first transmission beam in a second time resource. The second transmission beam is different from the first transmission beam, and the second time resource is different from the first time resource.

In some embodiments, the one or more DRS signals comprise channel state information reference signals (CSI-RS). In some embodiments, the one or more DRS signals include a Primary Synchronization Signal (PSS) for a Physical Cell Identity (PCI), a Secondary Synchronization Signal (SSS) for the same PCI, and a Common Reference Signal (CRS) for the same PCI. In some embodiments, all DRS signals are beamformed. However, in some embodiments, only a subset of DRS signals are beamformed.

In some embodiments, each of the at least two different time resources is a slot, a subframe, a symbol time, a frame, a Transmission Time Interval (TTI), or an interlace time.

In some embodiments, the at least two different time resources are at least two different DRS occasions, and transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting the same one or more DRS signals using the at least two different transmit beams in the at least two different DRS occasions.

In some embodiments, the at least two different time resources are at least two time resources within a same DRS occasion and transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting the same one or more DRS signals using the at least two different transmit beams in the at least two different time resources within the same DRS time.

In some embodiments, transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmit the same one or more DRS signals in accordance with a DRS transmit beam pattern that defines the at least two different transmit beams of the at least two different time resources in which the one or more DRS signals are to be transmitted. Further, in some embodiments, the DRS transmission beam pattern is a symmetric DRS transmission beam pattern. In other embodiments, the DRS transmit beam pattern is an asymmetric DRS transmit beam pattern. In some embodiments, the DRS transmission beam pattern is an aperiodic DRS transmission beam pattern.

In some embodiments, transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: determining to transmit the one or more DRS signals using a DRS transmit beam pattern; determining which DRS transmission beam pattern is to be used for transmitting the one or more DRS signals; and transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources in accordance with the DRS transmission beam pattern. Further, in some embodiments, deciding to transmit the one or more DRS signals using a DRS transmit beam pattern comprises: deciding to transmit the one or more DRS signals using a DRS transmit beam pattern based on one or more criteria selected from the group consisting of: a criterion to receive a request to transmit a beam pattern using the DRS from another network node; criteria for using a DRS to transmit a beam pattern when the TP uses or is expected to use beamforming; criteria to use a DRS transmit beam pattern when the number of transmit beams the TP is using or is expected to use is greater than a predefined threshold; a criterion to transmit a beam pattern using DRS when a large number of radio nodes are present in a coverage area of the TP; criteria to use the DRS to transmit a beam pattern when there are a limited number of different DRS resources available; criteria for a DRS to transmit a beam pattern to be used for a particular deployment scenario; a criterion to use the DRS to transmit a beam pattern when the system load is greater than a predefined threshold; criteria based on measurement performance; and a criterion to transmit a parameter based on one or more DRSs.

In some embodiments, transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmit the same one or more DRS signals in accordance with a DRS transmit beam pattern that defines the at least two different transmit beams of the at least two different time resources in which the one or more DRS signals are to be transmitted. The method further comprises: providing information to a wireless apparatus related to transmission of the one or more DRS signals in accordance with the DRS transmission beam pattern. In some embodiments, the information includes an indication that the TP is to transmit, or is expected to transmit, DRS signals according to a DRS transmission beam pattern. In some embodiments, the information includes an indication that the TP is to transmit, or is expected to transmit, the one or more DRS signals in accordance with the DRS transmission beam pattern. In some embodiments, the information includes information related to transmitting DRS signals in a DRS transmission beam pattern in a plurality of cells.

In some embodiments, transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmit the same one or more DRS signals in accordance with a DRS transmit beam pattern that defines the at least two different transmit beams of the at least two different time resources in which the one or more DRS signals are to be transmitted. The method further comprises: providing, to another network node, information related to transmission of the one or more DRS signals by the TP in the DRS transmission beam pattern.

In some embodiments, the method further comprises: receiving, from a wireless device, one or more measurements based on the one or more DRS signals transmitted using the at least two different transmission beams in the at least two different time resources; and correlating each of the one or more measurements with a respective beam of the at least two different transmit beams. Further, in some embodiments, transmitting the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmit the same one or more DRS signals in accordance with a DRS transmit beam pattern that defines the at least two different transmit beams of the at least two different time resources in which the one or more DRS signals are to be transmitted. Correlating each of the one or more measurements with the respective one of the at least two different transmit beams comprises: correlating each of the one or more measurements with the respective one of the at least two different transmit beams based on the known time resources in which the measurements were obtained and the DRS transmit beam pattern.

Embodiments of a TP for a cellular communication network are also disclosed. In some embodiments, a TP includes a transceiver, a processor, and a memory storing instructions executable by the processor, whereby the TP is operable to transmit the same one or more DRS signals via the transceiver using at least two different transmission beams in at least two different time resources. Each transmit beam is characterized by the direction in which it is transmitted.

In some embodiments, a TP for a cellular communication network is adapted to transmit the same one or more DRS signals using at least two different transmission beams in at least two different time resources. Each transmit beam is characterized by the direction in which it is transmitted. Further, in some embodiments, the TP is further adapted to perform a method of operation of a TP according to any of the embodiments described herein.

In some embodiments, a TP for a cellular communication network comprises: a DRS transmission module operable to transmit the same one or more DRS signals using at least two different transmission beams in at least two different time resources. Each transmit beam is characterized by the direction in which it is transmitted.

An embodiment of a computer program is also disclosed. In some embodiments, the computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out a method of operation of a TP according to any of the embodiments described herein. Further, in some embodiments, a carrier containing the above-mentioned computer program is disclosed, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

Embodiments of a non-transitory computer readable medium are also disclosed. In some embodiments, a non-transitory computer-readable medium stores software instructions that, when executed by a processor of a TP for a cellular communication network, cause the TP to transmit the same one or more DRS signals using at least two different transmission beams in at least two different time resources. Each transmit beam is characterized by the direction in which it is transmitted.

Embodiments of a method of operation of a wireless device in a cellular communication network are also disclosed. In some embodiments, a method of operation of a wireless device includes obtaining information related to DRS transmission configuration. The information related to DRS transmission configuration comprises at least one of the group consisting of: DRS transmission beam pattern information related to DRS transmission beam patterns used for one or more cells and measurement adaptation information for adapting one or more measurement procedures. The method further comprises the following steps: performing one or more measurements on one or more DRS signals in accordance with the information related to DRS transmission configuration; and using at least one of the one or more measurements for one or more radio operation tasks.

In some embodiments, the information related to DRS transmission configuration includes the DRS transmission beam pattern information, and the DRS transmission beam pattern information includes an indication of whether at least one TP for the one or more cells is to, or is expected to, transmit DRS signals according to a DRS transmission beam pattern.

In some embodiments, the information related to DRS transmission configuration comprises the DRS transmission beam pattern information, and the DRS transmission beam pattern information comprises an indication of a DRS transmission beam pattern to be used, or intended to be used, for transmitting DRS resources for at least one of the one or more cells.

In some embodiments, the information related to DRS transmission configuration further comprises at least one of the group consisting of: information related to physical resources in which a DRS signal is transmitted, a bandwidth of the DRS signal, a measurement bandwidth for the DRS signal, and a periodicity of DRS occasions.

In some embodiments, obtaining the information related to DRS transmission configuration comprises: obtaining the information related to DRS transmission configuration from a network node.

In some embodiments, obtaining the information related to DRS transmission configuration comprises: obtaining the information related to DRS transmission configuration based on one or more predefined rules.

In some embodiments, obtaining the information related to DRS transmission configuration comprises: autonomously obtaining the information related to DRS transmission configuration. In some embodiments, autonomously obtaining the information related to DRS transmission configuration comprises: autonomously detecting whether different beams are used for transmission in at least one of a group consisting of different DRS occasions and different time resources within a DRS occasion. In some embodiments, the method further comprises: transmitting the information related to DRS transmission configuration to at least one of a group consisting of a network node and another wireless apparatus.

In some embodiments, performing the one or more measurements comprises: adapting one or more measurement procedures based on the information related to DRS transmission configuration to perform the one or more measurements on the one or more DRS resources in accordance with the DRS transmission configuration information. Further, in some embodiments, performing the one or more measurements comprises: adapting one or more measurement procedures based on measurement adaptation information, and the measurement adaptation information comprises at least one of the group consisting of: a layer 3 filtering coefficient having a value set such that DRS measurements by the wireless apparatus are not averaged; and a time to trigger a parameter, the value of which is set such that the time to trigger a DRS reporting event in the wireless device is zero.

In some embodiments, adapting the one or more measurement procedures comprises at least one of the group consisting of: switching between a first measurement modality for use when the DRS transmission beam pattern is not used for DRS transmission and a second measurement modality for use when the DRS transmission beam pattern is used for DRS transmission; reporting up to M measurements on different DRS resources, but only obtaining M' < M measurements for the same time resource; and adapting at least one measurement procedure to detect and distinguish between different beams using the same DRS resource in different time resources.

In some embodiments, the one or more radio operation tasks comprise at least one of the group consisting of: performing a cell change, reporting at least one of the one or more measurements to a network node, reporting at least one of the one or more measurements to another wireless device, and determining a location of the wireless device.

In some embodiments, the one or more radio operation tasks comprise reporting at least one of the one or more measurements to a network node in association with an indication of timing resources during which the at least one of the one or more measurements was obtained.

In some embodiments, the method further comprises: signaling, to a network node, an indication of a capability of the wireless device to support transmitting DRS resources in a DRS transmit beam pattern.

Embodiments of a wireless apparatus for a cellular communication network are also disclosed. In some embodiments, a wireless device comprises a transceiver, a processor, and a memory storing instructions executable by the processor, whereby the wireless device is operable to: obtaining information related to DRS transmission configuration, the information related to DRS transmission configuration including at least one of the group consisting of: DRS transmission beam pattern information related to a DRS transmission beam pattern used for one or more cells; and measurement adaptation information used to adapt one or more measurement procedures. The wireless apparatus is further operable to perform one or more measurements on one or more DRS signals in accordance with the information related to DRS transmission configuration; and using at least one of the one or more measurements for one or more radio operation tasks.

In some embodiments, a wireless device for a cellular communication network is adapted to: obtaining information related to DRS transmission configuration, the information related to DRS transmission configuration including at least one of the group consisting of: DRS transmission beam pattern information related to a DRS transmission beam pattern used for one or more cells; and measurement adaptation information used to adapt one or more measurement procedures. The wireless device further performs one or more measurements on one or more DRS signals in accordance with the information related to DRS transmission configuration and uses at least one of the one or more measurements for one or more radio operation tasks. In some embodiments, the wireless device is further adapted to operate in accordance with any of the embodiments of the method of operation of a wireless device described herein.

In some embodiments, a wireless device for a cellular communication network comprises: an information obtaining module operable to obtain information related to a DRS transmission configuration, the information related to a DRS transmission configuration comprising at least one of the group consisting of: DRS transmission beam pattern information related to a DRS transmission beam pattern used for one or more cells; and measurement adaptation information used to adapt one or more measurement procedures. The wireless device further comprises: a measurement module operable to perform one or more measurements on one or more DRS resources in accordance with the information related to DRS transmission configuration; and a usage module operable to use at least one of the one or more measurements for one or more radio operation tasks.

Embodiments of a computer program are also disclosed. In some embodiments, the computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out a method of operation of a wireless device according to any of the embodiments described herein. Further, in some embodiments, a carrier containing the aforementioned computer program is disclosed, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

Embodiments of a non-transitory computer readable medium are also disclosed. In some embodiments, a non-transitory computer readable medium stores software instructions that, when executed by a processor of a wireless device for a cellular communication network, cause the wireless device to: obtaining information related to DRS transmission configuration; performing one or more measurements on one or more DRS resources in accordance with the information related to DRS transmission configuration; and using at least one of the one or more measurements for one or more radio operation tasks. The information related to DRS transmission configuration comprises at least one of the group consisting of: DRS transmission beam pattern information related to a DRS transmission beam pattern used for one or more cells; and measurement adaptation information used to adapt one or more measurement procedures.

Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the embodiments in association with the accompanying drawing figures.

Drawings

The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the present disclosure and, together with the description, serve to explain the principles of the disclosure.

Fig. 1 illustrates downlink physical resources in the third generation partnership project (3 GPP) Long Term Evolution (LTE);

fig. 2 shows a downlink subframe in 3GPP LTE;

fig. 3 illustrates Resource Elements (REs) used by Discovery Reference Signal (DRS) signals in a Physical Resource Block (PRB) pair;

fig. 4 and 5 illustrate some possible configurations of Discovery Measurement Timing Configuration (DMTC) or measurement gaps that satisfy constraints related to DRS signals and DRS occasions;

FIG. 6 illustrates one example of a cellular communication network in which embodiments of the present disclosure may be implemented;

fig. 7 is a flow chart illustrating operation of a Transmission Point (TP) according to some embodiments of the present disclosure;

fig. 8 is a more detailed illustration of a process for transmitting the same DRS signal on different transmit beams in different time resources, in accordance with some embodiments of the present disclosure;

fig. 9 is a flow chart illustrating operation of a TP according to some other embodiments of the present disclosure;

FIG. 10 is a flow chart illustrating operation of a wireless device according to some embodiments of the present disclosure;

fig. 11 illustrates operations of a wireless device and a TP according to some embodiments of the present disclosure;

FIG. 12 illustrates another example of a cellular communications network in which embodiments of the present disclosure may be implemented;

fig. 13 and 14 are block diagrams of wireless devices according to some embodiments of the present disclosure; and

fig. 15-17 are block diagrams of TPs according to some embodiments of the present disclosure.

Detailed Description

The embodiments set forth below represent information that enables those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

A network node: in some embodiments, the non-limiting term "network node" (also interchangeably referred to as node) is used generically and refers to any type of network node that communicates directly or indirectly with a wireless device (e.g., User Equipment (UE)) in a wireless communication network (e.g., a cellular communication network, such as, for example, a third generation partnership project (3 GPP) Long Term Evolution (LTE) network). The network node can be a radio network node (also referred to as radio access node) in a radio access network, a core network node in a core network or a node in a fixed part of a network. For example, the network node can be a network node serving a wireless device (e.g., UE), a network node neighboring a serving network node of the wireless device, or any network node in a core network or in a radio access network in a wireless communication system in which the wireless device operates. Examples of network nodes are base stations, multi-standard radio (MSR) radio nodes, such as MSR base stations, enhanced or evolved node bs (enbs), network controllers, radio network controllers, base station controllers, repeaters, donor nodes controlling repeaters, Base Transceiver Stations (BTSs), Access Points (APs), core network nodes (e.g., Mobile Switching Centers (MSCs), Mobility Management Entities (MMEs), etc.), operations and management (O & M) nodes, Operations Support Systems (OSS) nodes, self-organizing networks (SON) nodes, positioning nodes (e.g., evolved serving mobile location centers (E-SMLCs)), Minimization of Drive Tests (MDT) nodes, etc.

A wireless device: in some embodiments, the non-limiting term "wireless device" is used to refer to any type of wireless device that communicates with a wireless communication system. One example of a wireless device is a UE. The term "UE" is a non-limiting term used herein to refer to any type of wireless device that communicates over a radio interface with a network node in a cellular or mobile communication system. Examples of UEs include UEs in 3GPP LTE networks, target devices, device-to-device (D2D) UEs, Machine Type Communication (MTC) UEs, UEs with machine-to-machine (M2M) communication capabilities, Personal Digital Assistants (PDAs), ipads, tablets, mobile terminals, smart phones, Laptop Embedded Equipment (LEEs), Laptop Mounted Equipment (LMEs), Universal Serial Bus (USB) dongles, and so forth.

Discovery Reference Signal (DRS) or DRS signal: as used herein, the non-limiting term "DRS signal" is used interchangeably with the terms "DRS" and "discovery signal". As used herein, the non-limiting term "DRS signal" is any type of discovery signal transmitted in a wireless communication network, such as a cellular communication network. As one example, in a 3GPP LTE network, DRS signals are DRS signals transmitted by a Transmission Point (TP) during a DRS occasion, and DRS signals are Primary Synchronization Signals (PSS), Secondary Synchronization Signals (SSS), Common Reference Signals (CRS), channel state information reference signals (CSI-RS), Positioning Reference Signals (PRS), and the like, transmitted by the TP in the DRS occasion. DRS signals can be transmitted in a cell in DRS occasions (also referred to herein as "discovery occasions") with some periodicity (also referred to as DRS occasion periodicity or discovery occasion periodicity). A DRS occasion may contain a certain number of time resources (e.g., subframes) with DRS signals (e.g., between 1-6 subframes). Examples of DRS occasion periodicity include 40 milliseconds (ms), 80ms, and 160 ms. DRS may be identified by DRS index. The DRS index may be associated with a DRS configuration, such as one or more of its physical cell ID, scrambling identity, resource configuration (subcarriers in a subframe and those OFDM symbols carry DRSs), and its subframe offset (those subframes in a subframe in a DRS occasion carry DRSs).

DRS resource: as used herein, the term "DRS resource" (also referred to as "discovery resource") is a unique combination of DRS signals (e.g., a unique combination of PSS, SSS, CRS, and CSI-RS). In other words, a DRS resource corresponds to one DRS configuration. Each DRS configuration configures one DRS resource (e.g., containing PSS, SSS, and potentially one CSI-RS).

DRS timing: as used herein, the term "DRS occasion" includes one or more time resources (e.g., subframes) during which DRS signals are transmitted. DRS occasions are also referred to as "discovery occasions", "discovery signal transmission occasions", "discovery occasion reference signal occasions", "positioning occasions", "PRS occasions", and the like.

Time resource: in some embodiments, the non-limiting term "time resource" is used. As used herein, a "time resource" is any time unit in a wireless communication system (e.g., a cellular communication network). For example, the time resource can be a slot, a subframe, a symbol, a frame, a Transmission Time Interval (TTI), an interlace time, and the like.

Measurement: in some embodiments, the non-limiting term "measuring" is used. Embodiments are applicable to any type of measurement performed by a wireless device on any DRS signal. Examples of measurements that can be performed by a wireless device on DRS signals are cell search (also known as cell identity), Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), channel state information RSRP (CSI-RSRP) (as defined, for example, in section 5.1.20 of 3GPP TS 36.214 V12.2.0), CSI-RSRQ, Channel Quality Indication (CQI), CSI, UE receive-transmit (Rx-Tx) time difference, signal-to-interference-plus-noise ratio (SINR), DRS-SINR, and so forth. CSI-RSRQ on a linear scale is the ratio of CSI-RSRP to RSSI, where RSSI is the total received power at the UE, which contains all types of interference and noise. The measurements can be performed by the wireless device on one or more serving cells and/or on one or more neighbor cells. Measurements can also be performed on DRS signals transmitted by one or more TPs within the same cell, which can be a serving cell or a neighbor cell. Thus, one or more measurements made on a cell or network node are also interchangeably referred to as measurements made on a TP or TP signal.

Transmission or Transmission Point (TP): as used herein, the non-limiting term "TP" refers to a network node having one or more co-located antennas associated with a cell identity (PCI). A network node (e.g., an eNB or base station) may have a single TP or multiple distributed TPs. The TP can be a serving or neighboring TP. TPs may be interchangeably referred to as Remote Radio Heads (RRHs) and Remote Radio Units (RRUs), or base stations in the case of a single TP, or even all network nodes in a shared cell can be referred to as TPs.

Although the systems and methods disclosed herein may be applied to any wireless communication technology, embodiments of the present disclosure are described in the context of 3GPP LTE technology. In other words, the embodiments described below focus on 3GPP LTE. Therefore, 3GPP LTE technical terminology is sometimes used. However, embodiments may be applied to any Radio Access Technology (RAT) or multi-RAT system in which a wireless device receives and/or transmits signals (e.g., data), such as LTE Frequency Division Duplex (FDD)/Time Division Duplex (TDD), Wideband Code Division Multiple Access (WCDMA)/High Speed Packet Access (HSPA), global system for mobile communications (GSM)/enhanced data rates for GSM evolution (EDGE) radio access network (GERAN), WiFi, Wireless Local Area Network (WLAN), code division multiple access 2000 (CDMA 2000), and so forth.

A problem with using the DRS feature in a beamformed system is that the amount of available DRS resources is insufficient, as each node may have a large number of possible transmission beams, and each transmission beam is associated with a unique DRS resource. In a beamformed system, a network node may have a large number of antennas that can be used to generate several transmit beams in the same cell. One solution to providing a unique DRS resource for each transmit beam is to increase the number of DRS resources. However, increasing the number of DRS resources in a beamformed system would significantly increase the signaling overhead due to the potentially large number of transmit beams.

Embodiments of the present disclosure address the above-mentioned problems in beamforming systems. Embodiments of the present disclosure are directed to signaling information from a network node to a UE about a transmission beam (a.k.a. transmission beam) used for transmitting the same DRS signal using two or more transmission beams in different time resources, i.e., transmission beams using the same DRS resources. This signaling allows the UE to adapt its measurement procedure when measuring the DRS signal (e.g., averaging the samples used to obtain the result). The UE may also signal the time at which the DRS measurement is made to accompany the DRS (CSI-RSRP) based measurement and an identifier of the DRS configuration associated with the DRS measurement, such as a DRS index (which may be a CSI-RS ID identifying the CSI-RS configuration in some embodiments).

The measurement performance is enhanced due to the beam specific measurements (even when the network node uses a large number of beams). This in turn enhances UE mobility performance.

The density of reference signal structures developed for conventional deployment with existing systems (such as 3GPP LTE) can be high, such that many unnecessary interferences are generated when the deployment becomes dense. The reference signal may be transmitted even when no data is sent to the UE.

A set of reference signals transmitted at a much lower density in time for which they are intended to be used for small cells has been introduced in 3 GPP. Such signals are referred to as DRS signals (also known as discovery signals or DRSs), and the procedures associated with them are referred to as DRS procedures or discovery procedures.

Another motivation for DRS signals/procedures is to facilitate efficient measurement of received signal strength and quality (referred to as RSRP and RSRQ in 3 GPP) for different TPs within a cell. These TPs may be geographically separated (i.e., in separate geographic locations), but perform coordinated transmissions as a logically single cell entity.

In the present disclosure, a new application of DRS signals is used, where different DRS signals are used for different transmission beams transmitted from the same TP. The transmit beam is generated by an array of antenna elements from which the same signal is transmitted but with different adaptive phase shifts in order to steer the transmit beam in the desired direction while reducing interference towards other directions.

A TP can in principle generate an arbitrarily large set of beams or it can also use a limited set of beams. In general, the array of antenna elements may be two-dimensional or three-dimensional, and the set of transmit beams may have a pointing direction in azimuth and elevation, so-called two-dimensional (2D) beamforming.

The advantages of the embodiments of the present disclosure are readily recognized by one of ordinary skill in the art. These advantages include, but are not limited to:

allowing a much larger set of transmit beams (DRSs) to be used in the system, which is useful when a dense set of nodes, each employing beamforming, is used.

This solution enables the UE to know whether the transmission beam is the same or different in different time resources, e.g. in different DRS occasions. This enables the UE to adapt one or more measurement procedures.

Systems and methods related to a TP transmitting DRSs on multiple transmit beams are disclosed. Further, systems and methods related to performing measurements on DRS signals and adapting measurement procedures based on information related to DRS transmission configuration are also disclosed. In this regard, fig. 6 illustrates one example of a cellular communication network 10 in which embodiments of the present disclosure may be implemented. Note that the cellular communication network 10 is only one example and is to be understood as non-limiting. As shown, the cellular communication network 10 includes a macro node 12 (e.g., a base station such as, for example, an eNB) serving a macro cell 14 and a plurality of RRHs 16-1 to 16-3 (collectively and collectively referred to herein as RRHs 16 and individually as RRHs 16) serving respective small cells 18-1 to 18-3 (collectively and collectively referred to herein as small cells 18 and individually as small cells 18). The cellular communication network 10 is a shared cell deployment in which the macro cell 14 and the small cell 18 share the same cell Identity (ID) (e.g., the same physical cell ID (pci)). The macro node 12 and the RRHs 16 provide radio access to a plurality of wireless devices 20-1 through 20-4 (collectively referred to herein generally as wireless devices 20, and individually as wireless devices 20).

With respect to wireless device 20, cells 14 and 18 may be on a serving carrier (i.e., a serving cell of wireless device 20) or a non-serving carrier (i.e., a non-serving cell of wireless device 20). Examples of serving carriers are Primary Component Carrier (PCC) (also referred to as primary cell (PCell)) and Secondary Component Carrier (SCC) (also referred to as secondary cell (SCell)) in Carrier Aggregation (CA) (also referred to as multi-carrier), Primary and Secondary Component Carriers (PSCC) and SCC in Dual Connectivity (DC). Examples of non-serving carriers are inter-frequency carriers, inter-RAT carriers, etc. Note that measurements on non-serving carriers can be performed with or without measurement gaps.

In accordance with some embodiments of the present disclosure, one or more TPs (e.g., one or more macro-nodes 12 and/or one or more RRHs 16) each transmit a plurality of beams (transmit beams), and each transmit beam is associated with a DRS resource. Currently, in 3GPP LTE, only 96 unique DRS resources are supported in release 12 (Rel-12), and Rel-12 has been designed for networks with a rather small number of TPs, one DRS resource per TP, in a given area. Examples of smaller sets of TPs are 2 or 3. Specifically, as discussed above, considering that the DRS occasion may be up to 5 subframe lengths in the FDD frame structure, the maximum possible number of CSI-RS RE configurations is 96. This means that the maximum possible number of unique DRS resources is 96. Additionally, it should be noted that, at least in some embodiments, only CSI-RS is beamformed (i.e., PSS, SSS, and CRS may not be beamformed), while in other embodiments, both CSI-RS (if configured) and one or more other DRS signals (e.g., PSS, SSS, and/or CRS) are beamformed.

If each TP has multiple transmit beams, there is a need for even more than 96 DRS resources. Embodiments of the present disclosure relate to reusing DRS resources in time such that at time instant a DRS signals for a particular DRS resource with index Q are transmitted in transmission beam a and at another time instant B the same DRS signals (for the same DRS resource with index Q) are transmitted in another transmission beam B different from transmission beam a. The same DRS signals (i.e., DRS signals corresponding to the same DRS resources) may include DRS signals for the same identifier (e.g., PSS, SSS, or CRS for the same PCI (where a particular PCI is mapped to a particular PSS, SSS, or CRS, as will be appreciated by one of ordinary skill in the art)), CSI-RS for the same identifier for TPs transmitting CSI-RS, and so on.

Such transmitting the same DRS signals on at least two different transmission beams at two different times (i.e., in two different time resources) is referred to herein as a pattern. This pattern is more precisely referred to herein as the DRS transmit beam pattern. Within the DRS transmission beam pattern, the same DRS resources are used (i.e., the same DRS signals are transmitted such that PSS, SSS, and CSI-RS (if configured) occupy the same resource elements in the subframe containing the DRS, but do so in the two different subframes (e.g., having the same cell ID, TP ID, etc.). Embodiments may be applied to DRS transmission modes consisting of any number of transmission beams, such as transmission beam A, B, C, D, E, and so on.

The DRS transmission beam pattern includes transmitting the same one or more DRS signals in at least two different transmission beams (e.g., a and B) in at least two different time resources (e.g., two different DRS occasions). The DRS transmit beam pattern is also characterized by a reference time parameter. Examples of reference time parameters for DRS transmit beam patterns are the start time of the pattern, the length of the pattern in time, the end time of the pattern, etc. The start time of a mode can be expressed in terms of a frame number or an absolute or global reference time, such as a Global Navigation Satellite System (GNSS) reference time (e.g., a Global Positioning System (GPS) reference time). An example of a frame number as a reference time is a System Frame Number (SFN), which repeats in a cycle (e.g., after every 1024 radio frames). Accordingly, SFN can vary from 0 to 1023. For example, the start reference time of the pattern can be configured by the network node, or can be predefined. Examples of predefined SFNs are SFN =0, SFN =512, etc.

As an example, the pattern of beams a and B using the same DRS signal is transmitted in two consecutive time resources and repeated in subsequent time resources, i.e., in subsequent DRS occasions. Typically, beams having the same characteristics (e.g., direction, beam width, etc.) are repeated periodically. For example, assume that the same DRS signal can be transmitted in 4 different beams (i.e., A, B, C and D) in 4 consecutive DRS occasions (i.e., T0, T1, T2, and T3, respectively). As an example, each DRS occasion contains 1 subframe, and each DRS occasion occurs periodically every 40 ms. The same DRS signals (e.g., PSS/SSS/CRS, CSI-RS, etc.) are transmitted in the same direction as transmission beams A, B, C and D in the subsequent DRS occasion (i.e., T4, T5, T6, and T7, respectively). This is an example of a symmetric periodic pattern with a period of 4 DRS occasions and where within each pattern period all possible beams are transmitted with equal probability and the content of the pattern is the same in all pattern periods.

Examples of symmetric periodic DRS transmit beam patterns are described below by (1) and (2):

DRS timing: [ { T0, T1, T2, T3}, { T4, T5, T6, T7}, … … ] (1)

Beam/opportunity: [ { A, B, C, D }, { A, B, C, D } … … ] (2)

Another example of a symmetrical periodic DRS transmit beam pattern is described below by (3) and (4). In this case, each beam repeats on two consecutive DRS occasions over a pattern period equal to 8.

DRS timing: [ { T0, T1, T2, T3, T4, T5, T6, T7}, { T8, T9, T10, T11, T12, T13, T14, T15}, … ] (3)

Beam/opportunity: [ { A, A, B, B, C, C, D, D }, { A, A, B, B, C, C, D, D }, … ] (4)

The periodic pattern can also be asymmetric (asymmetric periodic DRS transmit beam pattern), where the pattern period is the same, but the pattern content in different periods can be different. Examples of such patterns with a period of 6 DRS occasions are expressed below by (5) and (6):

DRS timing: [ { T0, T1, T2, T3, T4, T5}, { T6, T7, T8, T9, T10, T11} … … ] (5)

Beam/opportunity: [ { A, A, B, B, C, D }, { C, D, D, D, A, B } … … ] (6)

In some embodiments, the DRS transmit beam pattern can also be aperiodic, where the periodicity can change after each pattern. Examples of such modes are expressed below by (7) and (8):

DRS timing: [ { T0, T1, T2}, { T3, T4, T5, T6, T7}, { T8, T9, T10, T11} … … ] (7)

Beam/opportunity: [ { A, B, C }, { B, C, D, D, A }, { C, D, D, D, A } … … ] (8)

In yet another example of a DRS transmit beam pattern, different beams using the same DRS resources (i.e., transmitting the same DRS signals) are used in different time resources (e.g., different subframes) within the same DRS occasion. In one implementation, the same DRS transmission beam pattern can be used in different DRS occasions. However, in some implementations, different DRS transmit beam patterns can also be used in different DRS occasions. Examples of such DRS transmit beam patterns (i.e., different beams within the same DRS time frame) are expressed below by (9) and (10). In this example, assume that one DRS occasion contains 4 time resources (e.g., 4 subframes) containing 4 different beams A, B, C and D:

time resources within one DRS epoch: { t0, t1, t2, t3} (9)

Beam/time resource: { A, B, C, D } (10)

In yet another example of a DRS transmit beam pattern within a DRS occasion, different beams on the same DRS resource are used in different time resources (e.g., different subframes) within the same DRS occasion, but some of them are repeated. Examples of such DRS transmission beam patterns are expressed below by (11) and (12). In this example, assume that one DRS occasion contains 6 time resources (e.g., 6 subframes) containing 4 different types of beams A, B, C and D. However, 2 of the 4 beams are transmitted twice:

time resources within one DRS epoch: { t0, t1, t2, t3, t4, t5} (11)

Beam/time resource: { A, B, B, C, D, D } (12)

In some embodiments, it is decided by a network node (e.g., macro node 12) whether a DRS transmit beam pattern should be used or a DRS transmit beam pattern is not needed (i.e., as in conventional or existing systems) to transmit DRS signals. When using a DRS transmit beam pattern for DRS transmission, it is also decided by the network node which type of DRS transmit beam pattern to use for transmitting DRS signals. The DRS signal is ultimately used by wireless device 20 to perform measurements on the DRS signal.

According to some embodiments, the network node may decide to generate a DRS transmission pattern (i.e. to transmit DRS signals according to the DRS pattern), and also decide the type of DRS transmission pattern based on one or more of the following criteria:

criteria related to receiving a request from another network node, e.g. the serving eNB requesting the TP to use a DRS transmission mode and/or a type of DRS transmission mode;

criteria related to when beamforming is being used or expected to be used by the network node (e.g., using the DRS transmission mode when beamforming is being used or expected to be used);

a criterion related to the number of transmit beams being used or expected to be used by the network node (e.g., using the DRS mode when the number of beams being used or expected to be used by the network node is greater than a threshold);

a criterion related to the number of radio nodes in the coverage area (e.g., using the DRS mode when there are a large number (e.g., more than a threshold number) of radio nodes in the coverage area (e.g., a large number of TPs per shared cell, i.e., having the same PCI));

criteria related to the number of available DRS resources and/or the number of unavailable DRS resources (e.g., using a DRS transmission pattern when there is a limited number (e.g., less than a threshold number) of different DRS resources available, or when there is some threshold number of DRS resources that cannot be used);

criteria related to the deployment scenario (e.g., using DRS transmission pattern in a particular deployment scenario, such as a cell serving a high-rise building, with wireless devices 20 distributed in both the azimuth and elevation directions);

a criterion related to system load (e.g., using DRS transmission mode when system load is high (e.g., a large number of wireless devices 20 in a cell));

criteria related to measurement performance: to enable the wireless device 20 to achieve better measurement accuracy, the network node may use a symmetric periodic pattern, where the same beam is repeated more than once in the same pattern period; and/or

Criteria related to DRS transmission parameters. For example, if the DRS bandwidth is greater than a threshold (e.g., 50 Resource Blocks (RBs) or more), the network node may use a symmetric periodic pattern in which no identical beams are repeated in the same pattern period.

In some embodiments, a network node (e.g., macro node 12) may also transmit information to one or more wireless apparatuses 20 when initiating DRS transmission according to the DRS transmission mode. This information is used to inform the wireless apparatus 20 that the network node is transmitting or expects to transmit DRSs according to a DRS transmission mode (in general) or according to a specific transmission mode. The network node may also send correspondence information to wireless device 20 (i.e., regarding termination of transmission of DRS signals according to the DRS transmission mode) when the DRS transmission according to the DRS transmission mode is ceased.

In one example, the information may include an indicator indicating whether the network node is performing the following:

transmitting (or anticipating transmission) DRS signals using (according to) a DRS transmission beam pattern; or

Stopping (or anticipatorily stopping) ongoing DRS transmission employing (according to) the DRS transmission beam pattern.

In another example, the information may provide at least some indication that a DRS transmit beam pattern is being used or is expected to be used or is being ceased for transmitting DRS signals. Examples of such information relating to the pattern are:

a predefined identifier of one of a plurality of predefined DRS transmission beam patterns and a pattern reference time, such as a start time of the pattern, e.g. SFN = 4;

partial or complete information about the schema itself. This may include one or more of: a mode reference time (such as a start time of a mode), a mode periodicity, a mode type (e.g., periodic or aperiodic, etc.), a number of distinct or different beams used in the same mode for the same DRS resource, etc.

Any of the information mentioned above may be associated with one or more cells, such as one or more neighbor cells and/or one or more serving cells for wireless device 20. For example, the network node may signal information for multiple cells to the wireless device 20, thereby enabling the wireless device 20 to perform measurements on multiple cells. In some embodiments, the information signaled for each cell may also include cell ID and/or cell-related information, such as PCI, TP ID, etc. In some embodiments, the signaled information may be common to multiple cells, e.g., the same information may apply to all cells on the same carrier frequency. In some embodiments, the signaled information may be common to two or more carrier frequencies, e.g., the same information may apply to all cells on the serving carrier frequency and all cells on one or more non-serving carrier frequencies (such as inter-frequency carriers).

The network node may transmit the above-mentioned information to the wireless device 20 using higher layer signaling, such as Radio Resource Control (RRC) or Medium Access Control (MAC) signaling. The network node may transmit this information in a broadcast message for all or a group of wireless devices 20 in the respective cell, or to a particular wireless device 20 in a wireless device specific (a.k.a. dedicated) message. The wireless devices 20 may use this information to adapt their measurement procedures as described below.

In accordance with some embodiments of the present disclosure, a network node may also transmit corresponding information to one or more other network nodes (e.g., neighboring network nodes) when initiating DRS transmission according to a DRS transmission mode, or when terminating ongoing DRS transmission according to a DRS transmission mode. The content of the information regarding starting or stopping the DRS transmission beam pattern can be the same as the content of the information transmitted to wireless device 20 (which was described above). A network node receiving this information may use this information for one or more tasks. Examples of such tasks are: creating its own DRS transmission mode; deciding whether to transmit a DRS signal according to a DRS transmission mode; and informing the wireless apparatus 20 in the cell about the DRS transmission mode used in the neighboring network node, etc.

Fig. 7 is a flow chart illustrating operation of a TP (e.g., one of the macro-nodes 12 or RRHs 16 of fig. 6) in accordance with some embodiments of the present disclosure. The process of fig. 7 illustrates at least some embodiments described herein. Note that the dashed boxes represent optional steps that may or may not be included in the process, depending on the embodiment. As shown, in some embodiments, a TP receives capability information from one or more wireless apparatuses 20 indicating whether the wireless apparatuses 20 have the capability to perform measurements, e.g., on DRS signals transmitted according to a DRS pattern (step 100).

The TP transmits the same DRS signals (e.g., according to a DRS transmission beam pattern) using at least two different transmission beams in at least two different time resources, as described above (step 102). In some embodiments, the transmitting in step 102 comprises: deciding whether a DRS transmission beam pattern is to be used (step 102A); deciding a DRS transmission beam pattern to be used (e.g., a type of DRS transmission beam pattern) (step 102B); and transmitting the same DRS signals on at least two different beams in at least two different time resources in accordance with a DRS transmit beam pattern (step 102C), as described above.

As shown in fig. 8, step 102 or step 102C includes, at least in some embodiments: DRS signals are transmitted on the first transmission beam but not on (at least) the second transmission beam in the first time resource (e.g. in the first DRS occasion) (step 200). The TP transmits the same DRS signals on the second transmission beam but not on (at least) the first transmission beam in a second time resource (e.g., a second DRS occasion) (step 202). The first and second transmission beams are different transmission beams (i.e., have different beam directions), and the first and second time resources are different time resources (e.g., different DRS occasions). Additional similar steps may be performed if more than two transmission beams and/or more than two time resources are included in the DRS transmission beam pattern. Using this procedure, for example when DRS signals are transmitted on a first transmission beam in a first time resource, a TP does not transmit the same DRS signals on a second transmission beam and potentially on any other transmission beam. In particular, when DRS signals are transmitted on a first transmission beam in a first time resource, the TP does not transmit the same DRS signals on any other transmission beam (which would negatively impact the ability of the wireless device to perform measurements on the DRS signals transmitted on the first transmission beam). In the same manner, when the same DRS signals are transmitted on the second transmission beam in the second time resource, the TP does not transmit the same DRS signals on the second transmission beam and potentially on any other transmission beam.

Returning to fig. 7, in some embodiments, the TP signals or otherwise provides information related to the DRS transmission configuration to wireless apparatus 20 and/or another network node (step 104), as described above. In some embodiments, the TP receives one or more measurements from wireless apparatus 20 based on the transmitted DRS signals and correlates the measurements with the respective transmission beams (step 106). As discussed in detail below, in some embodiments, an indication of the time resource for which the measurement was obtained is provided to, or associated with, the measurement. This timing information can then be used together with the DRS transmit beam pattern to determine the transmit beam to which to apply the measurements. Examples of measurements that can be received from the wireless apparatus 20 are cell searches (also known as cell identifications), such as measurements of RSRP, RSRQ, CSI-RSRP, CSI-RSRQ, CQI, CSI, UE receive-transmit time difference, SINR, DRS-SINR, and so forth.

In some embodiments, the TP uses the measurements (step 108). For example, a TP may use measurements received from wireless apparatus 20 by selecting one of the reported beams (identified by the DRS identity) from wireless apparatus 20 and transmitting a downlink shared data channel to wireless apparatus 20 using the same beam as used for the DRS beam for which wireless apparatus 20 has provided the measurement report.

Fig. 9 is a flow chart illustrating operation of a TP according to some embodiments of the present disclosure. As shown, the TP decides that the DRS transmit beam pattern is not to be used for transmitting DRS signals (step 300). In making this determination, the TP stops transmitting DRS signals in the DRS transmission beam pattern (step 302) and signals an indicator to wireless device 20 indicating the stop (step 304), as described above.

Embodiments related to the operation of wireless device 20 are also disclosed. In particular, systems and methods are disclosed relating to performing measurements at a wireless apparatus 20 using DRS signals transmitted by a TP according to the above-described embodiments (e.g., according to a DRS transmission beam pattern). In some embodiments, the method of operation of the wireless device 20 includes the following two steps:

wireless apparatus 20 obtains information at least about (i.e. related to) the DRS transmission configuration, which includes at least information about one or more DRS transmission beam patterns used in one or more cells (i.e. information about the patterns described above); and

the wireless device 20 uses the obtained information for performing one or more measurements on one or more DRS signals.

After performing the one or more measurements, wireless device 20 may use the one or more measurements for one or more radio operation tasks. Examples of such radio operation tasks are:

perform cell change. Examples of cell changes are handover, cell selection, cell reselection, RRC connection release with redirection, etc.;

transmit the measurement results to the network node (e.g., TP). Wireless device 20 may send the measurement results using one or more of the following mechanisms: periodically, a basis for event triggering, and a periodic basis for event triggering;

if the wireless device 20 is D2D capable (a.k.a. the wireless device 20 is proximity services (ProSe) capable), the measurement result is transmitted to another wireless device 20. Wireless device 20 may send the measurement results using one or more of the following mechanisms: periodically, a basis for event triggering, and a periodic basis for event triggering;

the measurement results are used to determine the location of the wireless device 20 (i.e., determine the wireless device location).

The obtained information on the DRS transmission configuration may further contain additional data or content related to the DRS. For example, the additional information may relate to physical resources on which the DRS signal is transmitted. Examples of physical resources are time resources containing DRS signals (e.g., number of subframes per DRS occasion), bandwidth of DRS signals, measurement bandwidth of DRS signals, periodicity of DRS occasions, etc. Wireless device 20 may obtain any information regarding the DRS transmission configuration by one or more of the following means:

in one exemplary implementation, wireless device 20 may obtain the information by receiving the information from a network node (e.g., a TP), as described above.

In another exemplary implementation, wireless device 20 may obtain the information based on one or more predefined rules and/or information;

in yet another exemplary implementation, the wireless device 20 may obtain this information autonomously. For example, wireless device 20 may autonomously detect whether a beam is the same or different in different DRS occasions and/or in different time resources within the same DRS occasion. The wireless device 20 may detect the above situation, for example, by detecting the angle of arrival (AoA) of the signal. In the case of different beams, wireless device 20 may detect changes in signal strength and/or AoA of the signal in different DRS occasions and/or time resources per DRS occasion.

Wireless apparatus 20 may also transmit such autonomously obtained information to a network node and/or to another wireless apparatus 20 if wireless apparatus 20 autonomously detects one or more parameters related to the DRS transmission configuration (e.g., number of beams per DRS occasion, etc.).

To perform one or more measurements on the DRS signals, wireless apparatus 20 may adapt one or more measurement procedures based on the obtained information related to the DRS transmission configuration. For example, when the same DRS signals are used in different beams in different time resources (e.g., different DRS occasions) and/or in different time resources in the same DRS occasion, adaptation of one or more measurement procedures will allow wireless apparatus 20 to perform measurements. The adaptation may also depend on the type of information related to the DRS transmission configuration obtained by wireless device 20. The adaptation may also depend on the type of DRS transmission beam pattern used by one or more cells on which wireless apparatus 20 performs one or more measurements.

Some examples of such adaptations of the measurement procedure in the wireless device 20 are now described. One example, such as adaptation, is to switch between the first measurement mode and the second measurement mode based on the obtained information related to the DRS transmission configuration. In one example, in a first measurement mode, the wireless device 20 uses a first number of measurement samples averaged over a layer 1 (L1) measurement period to obtain a measurement result, while in a second measurement mode, the wireless device 20 uses a second number of measurement samples averaged over an L1 measurement period to obtain a measurement result. For example, if the DRS is used to transmit the beam pattern, wireless device 20 uses a first measurement mode in which only one sample is used to obtain the measurement results. However, if the DRS transmit beam pattern is not used, then wireless device 20 uses a second measurement regime in which two or more samples in different DRS occasions are used to obtain measurements. In another example of the first measurement approach, wireless device 20 may use two or more measurement samples, but only measurement samples on DRS signals transmitted using the same beam in different time resources and/or DRS occasions. In yet another example, when using the first measurement modality, the wireless device 20 performs measurements over an L1 measurement period that is shorter than the L1 measurement period for measurements with the second measurement modality.

In some embodiments, wireless device 20 associates the measurement results with at least the timing related to the DRS transmission. For example, after a measurement, when the wireless apparatus 20 transmits a measurement report to a network node (e.g., a TP, such as a macro node 12 (e.g., eNB)), the wireless apparatus 20 reports the measured value, DRS index Q, and, in addition, the time of the measurement (a or B). In some embodiments, the DRS index includes an identifier for the CSI-RS, such as the MeasCSI-RS-Id-r12 information element in 3GPP Technical Specification (TS)36.331 section 6.3.5 (release 12.5.0). In one embodiment, the time of day is given by an SFN or by any other frame number or group of frame numbers. In one aspect of this embodiment, the time of reporting is a start time (or an end time) if the same DRS is transmitted in the same beam at multiple times. For example, if the DRS signal on which the measurements are made and the SFN for that DRS occasion is 4, then wireless device 20 signals the measurements and at least SFN = 4. In another example of this embodiment, the timing instances are timed by disabling the cross-frame or sub-frame averaging of DRS measurements at the physical layerAnd (4) supplementing. This disabling may be signaled to the wireless device 20 by higher layers, such as RRC signaling. This disabling may further set the layer 3 (L3) filtering of DRS measurements to 0, i.e., the variables in section 5.5.3.2 of 3GPP Technical Specification (TS)36.331 (release 12.5.0)aIs arranged asa And = 1. Still further, if event-triggered DRS reporting is configured, the disabling may also set the time used to trigger the event to 0, i.e., the information element from 3GPP TS 36.331 (release 12.5.0) section 6.3.5TimeToTriggerIs arranged asTimeToTrigger = ms 0. In this way, the physical or higher layer filtering of the trigger delay or DRS measurements will not increase the temporal ambiguity of when the measurements occurred, and the network will be able to better identify which beam was transmitted.

As another example of adaptation that may be performed by wireless apparatus 20, in some embodiments, wireless apparatus 20 is allowed to report M measurements of different DRS signals, but only M' < M measurements are obtained at the same time index. With this solution, a network node (e.g., eNB) may transmit beams from different TPs at different times, and thereby obtain DRS measurements from multiple TPs. If this constraint is not to be imposed, wireless device 20 may report only measurements for the beam at the TP closest to wireless device 20 (i.e., the strongest received signal). Alternatively, a network node (e.g., eNB) may transmit DRS beams in different sectors of a cell at different times for the same reasons with respect to different TPs.

As another example, in some embodiments, wireless apparatus 20 may adapt its procedures to be able to detect different beams that use the same DRS resource (i.e., transmit the same DRS signals) in different time resources (i.e., in different DRS occasions and/or DRS time resources) and distinguish between the beams. For example, based on this detection, wireless device 20 may use the performed measurements to identify the N number of measurements having the N most distinct beams (e.g., those having the most distinct directions in vertical and/or azimuth). Wireless device 20 may use N such measurements for one or more radio operation tasks, e.g., for cell change, reporting N measurements with the N most distinct beams to a network node and/or to another wireless device 20, for positioning, etc.

The wireless device 20 may adapt one or more of the above measurement procedures based on one or more of:

indications or requests received from the network node:

autonomous determination of the wireless device 20. Wireless device 20 may also perform adaptation to conform to one or more predefined requirements;

one or more predefined rules specified in the standard. The predefined rules may also be expressed in terms of one or more predefined requirements.

For example, the wireless device 20 may have to adapt one or more measurement procedures in order to meet one or more predefined wireless device requirements (a.k.a. measurement requirements), Radio Resource Management (RRM) requirements, mobility requirements, positioning measurement requirements, etc., related to wireless device measurements. Examples of wireless device requirements related to wireless device measurements are measurement time, measurement reporting time or delay, measurement accuracy (e.g., RSRP/RSRQ accuracy), number of cells to be measured at the measurement time, etc. Examples of measurement times are L1 measurement periods, cell identification times or cell search delays, Cell Global Identity (CGI) acquisition delays, etc.

According to another aspect, the procedures in the wireless device 20 may include: one or more sets of information relating to capabilities associated with obtaining a DRS transmit beam pattern and making one or more measurements using the DRS transmit beam pattern are signaled to a network node. This is caused by the fact that: all wireless apparatuses 20 may or may not be able to obtain and use DRS transmission beam patterns for measurements, or may be able to obtain and use DRS transmission beam patterns of only a particular type. Based on such received wireless device capabilities, the network node may decide whether to configure the DRS transmit beam pattern for wireless device 20. The network node may also use additional information in the wireless device capability to decide on the actual DRS transmission beam pattern to be configured in the cell. The network node may also signal the received wireless device capability information to another network node. The network node may acquire wireless device capabilities from wireless device 20 and/or from another network node containing such information.

Fig. 10 is a flowchart illustrating operations of wireless device 20 according to some embodiments of the present disclosure. The process of fig. 10 illustrates at least some embodiments described herein. Note that the dashed boxes represent optional steps that may or may not be included in the process, depending on the embodiment. As shown, in some embodiments, wireless apparatus 20 transmits capability information to a network node indicating whether wireless apparatus 20 has the capability to obtain and transmit a beam pattern using DRS (step 400), as described above.

Wireless device 20 obtains information related to DRS transmission configuration for one or more cells (step 402). As described above, this information includes DRS transmit beam pattern information and/or measurement adaptation information for one or more cells. The measurement adaptation information may include, for example: an L3 filter coefficient whose value is set such that DRS measurements made by wireless device 20 are not averaged; and/or the time to trigger a parameter whose value is set such that the time to trigger a DRS reporting event in wireless apparatus 20 is 0. This information may be obtained by the wireless device 20 in any suitable manner, such as, for example, from a network node, from predefined rules and/or predefined information, and/or autonomously. In some embodiments, wireless device 20 transmits the obtained information, or some subset thereof, to a network node or another wireless device 20, step 404.

Based on the obtained information, wireless apparatus 20 performs one or more measurements on DRS signals transmitted by one or more TPs, as described above (step 406). Performing the measurement may include adapting one or more measurement procedures. For example, as described above, such adaptation may be to switch between two or more measurements, to report only M' < M measurements obtained at the same time, and/or to detect and distinguish between different beams using the same DRS resource in different time resources.

Wireless device 20 uses the measurements to perform one or more radio operation tasks (step 408). As described above, the one or more radio operation tasks may include, for example: perform a cell change, report (i.e., transmit) measurements to a network node, report (i.e., transmit) measurements to another wireless device 20, and/or determine a location of wireless device 20.

Fig. 11 illustrates operations of TP 22 and wireless device 20 according to some embodiments of the present disclosure. As shown, TP 22 transmits the same DRS signals using at least two different transmission beams in at least two different time resources, e.g., in a DRS transmission beam pattern (step 500), as described above. In some embodiments, TP 22 transmits information related to the DRS transmission configuration for one or more cells to wireless apparatus 20, as described above (step 502). Wireless apparatus 20 obtains information related to the DRS transmission configuration (step 504) and, based on this information, performs one or more measurements on the DRS signals transmitted by TP 22 (step 506). The wireless device 20 then uses the measurements, as described above (step 508).

Although the described solution may be implemented in any suitable type of telecommunications system that supports any suitable communication standard and uses any suitable components, particular embodiments of the described solution may be implemented in an LTE network 24, such as the LTE network shown in fig. 12. As shown in fig. 12, an example LTE network 24 may include: one or more instances of wireless device 20, which are also referred to herein as wireless communication devices 20 (e.g., a conventional UE or MTC/M2M UE); and one or more TPs 22 (e.g., radio access nodes such as, for example, RRHs 16 and/or macro-nodes 12 of fig. 6) capable of communicating with the wireless device 20; together with any additional elements suitable for supporting communication between wireless devices 20 or between a wireless device 20 and another communication device, such as a landline telephone. Although the illustrated wireless devices 20 may represent communication devices including any suitable combination of hardware and/or software, these wireless devices 20 may represent devices in particular embodiments, such as the example wireless device 20 illustrated in more detail by fig. 13 and 14. Similarly, although the illustrated TP 22 may represent a network node containing any suitable combination of hardware and/or software, these nodes may represent apparatus such as the example TP 22 shown in more detail by fig. 15-17 in particular embodiments.

As shown in fig. 13, the example wireless device 20 includes a processor 26 (e.g., processing circuitry such as, for example, one or more Central Processing Units (CPUs), one or more Application Specific Integrated Circuits (ASICs), one or more Field Programmable Gate Arrays (FPGAs), and/or the like), a memory 28, a transceiver 30, and an antenna 32. In particular embodiments, some or all of the functionality described above as being provided by UE, MTC or M2M devices and/or any other type of wireless device 20 may be provided by processor 26 executing instructions stored on a computer-readable medium, such as memory 28 shown in fig. 13. Alternative embodiments of wireless device 20 may include additional components than those shown in fig. 13, which may be responsible for providing certain aspects of the device's functionality, including any of the functionality described above and/or any functionality necessary to support the solution described above.

Fig. 14 shows a wireless device 20 according to some other embodiments of the present disclosure. As shown, wireless device 20 includes an optional capability transfer module 34, an information acquisition module 36, a measurement module 38, and a usage module 40, each of which is implemented in software. The optional capability transfer module 34 operates to transfer capability information, for example, to a network node, as described above. Information obtaining module 36 operates to obtain information related to DRS transmission configuration, as described above. The measurement module 38 operates to perform measurements in accordance with the obtained information, as described above. The usage module 40 operates to perform one or more radio operation tasks using the measurements, as described above.

As shown in fig. 15, an example TP 22 (e.g., a radio access node such as macro node 12 or RRH 16) includes a processor 42 (e.g., processing circuitry such as, for example, one or more CPUs, one or more ASICs, one or more FPGAs, and/or the like), memory 44, a transceiver 46, and an antenna 48. As discussed above, in the embodiments described herein, the antenna 48 includes multiple antennas. In addition, the TP 22 includes a network interface 50 that enables communication with other network nodes (e.g., nodes in a core network). In particular embodiments, some or all of the functionality described above as being provided by a network node may be provided by processor 42 executing instructions stored on a computer-readable medium, such as memory 44 shown in fig. 15. Alternative embodiments of TP 22 may include additional components responsible for providing additional functionality, including any of the functionality identified above and/or any functionality necessary to support the above-described solution.

Fig. 16 is a schematic block diagram illustrating a virtualized embodiment of a TP 22 (e.g., a virtualized embodiment of a network node such as a radio access node) in accordance with some embodiments of the present disclosure. As used herein, a "virtualized" network node is a network node in which at least part of the functionality of the network node is implemented as a virtual component (e.g., via a virtual machine executing on a physical processing node in the network). As shown, TP 22 includes a processor 42, a memory 44, and a network interface 50, as well as a transceiver 46 coupled to an antenna 48, as described above. In this example, the processor 42, memory 44, and network interface 50 are implemented in a baseband unit 52, the baseband unit 52 being connected to the transceiver 46, e.g., via an optical cable or the like. The baseband unit 52 is connected via the network interface 50 to one or more processing nodes 54, the processing nodes 54 being coupled to or included as part of a network 56. Each processing node 54 includes one or more processors 58 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 60, and a network interface 62.

In this example, functions 64 of TP 22 described herein are implemented at the one or more processing nodes 54 or distributed across baseband unit 52 and the one or more processing nodes 54 in any desired manner. In some particular embodiments, some or all of the functionality 64 of TP 22 described herein is implemented as virtual components executed by one or more virtual machines implemented in a virtual environment hosted by processing nodes 54. As will be appreciated by those of ordinary skill in the art, additional signaling or communication between the processing node 54 and the baseband unit 52 is used in order to carry out at least some of the desired functions. In particular, in some embodiments, baseband unit 52 may not be included, in which case transceiver 46 communicates directly with processing node 54 via an appropriate network interface.

Fig. 17 shows a TP 22 according to some other embodiments of the present disclosure. As shown, TP 22 includes an optional capability receiving module 66, an optional information transmitting module 68, a DRS transmitting module 70, and an optional measurement receiving and using module 72, each of which is implemented in software. In some embodiments, capability receiving module 66 operates to receive capability information from wireless device 20. Information transfer module 68 operates to transfer information related to the DRS transfer configuration for one or more cells to wireless apparatus 20, as described above. DRS transmission module 70 operates to transmit DRS signals, as described above. Measurement reception and usage module 72 operates to receive and use measurements from wireless device 20, as described above.

Embodiments of the present disclosure can be realized in hardware, software, or a combination of hardware and software. Embodiments can be implemented as a computer program tangibly embodied on a computer program product, hardware memory, or other structure. Embodiments may be implemented on hardware modules, software modules, or a combination of hardware and software modules.

The following acronyms are used throughout this disclosure:

2D two-dimensional

3GPP third Generation partnership project

AAS active antenna System

Angle of arrival of AOA

AP Access Point

ASIC specific integrated circuit

BTS base Transceiver station

CA carrier aggregation

CDMA

CGI cell Global identity

CPU central processing unit

CQI channel quality indication

CRS common reference Signal

CSI channel state information

CSI-RS channel state information reference signals

D2D device to device

DC Dual connectivity

DMTC discovery measurement timing configuration

DRS discovery reference signal

Downlink part of DwPTS special subframe

EDGE enhanced data Rate GSM evolution

eNB enhancements or evolved node Bs

E-SMLC evolved serving mobile location center

FDD frequency division Duplex

FPGA field programmable Gate array

GERAN GSM enhanced data Rate GSM evolution radio Access network

GNSS Global navigation satellite System

GPS global positioning system

GSM Global System for Mobile communications

HSPA high speed packet Access

ID identity

LEE laptop embedded device

LME laptop mounted equipment

LTE Long term evolution

M2M machine-to-machine

MAC media access control

Minimization of MDT drive tests

MIMO multiple input multiple output

MME mobility management entity

Ms

MSC Mobile switching center

MSR multistandard radio

MTC machine type communication

Non-zero power of NZP

O & M operations and management

OFDM orthogonal frequency division multiplexing

OSS operation support System

PBCH physical broadcast channel

PCC Primary component Carrier

PCell Primary cell

PCI physical cell identity

PDA personal digital assistant

PRB physical resource Block

ProSe proximity services

PRS positioning reference signals

PSCC Primary and Secondary component Carrier

PSS Primary synchronization Signal

RAT radio access technology

RB resource Block

RE resource elements

Rel-12 edition 12

RF radio frequency

RRC radio resource control

RRH remote radio head

RRM radio resource management

RRU remote radio unit

RSRP reference signal received power

RSRQ reference Signal received quality

RSSI received signal strength indication

SCC secondary component carrier

SCell Secondary cell

SFN System frame number

SINR Signal to interference plus noise ratio

SON self-organizing nodes

SSS secondary synchronization signal

TDD time division duplexing

TP transfer Point

TS technical Specification

TTI Transmission time Interval

UE user Equipment

USB Universal Serial bus

VCID virtual or configurable cell identity

WCDMA wideband code division multiple Access

WLAN Wireless local area network

ZP zero power

Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.

Claims

1. A method of operation of a transmission point (22) in a cellular communications network (10), comprising:

transmitting (102) the same one or more discovery reference signals, DRS, signals from the transmission point (22) using at least two different transmission beams in at least two different time resources, each transmission beam being characterized by a direction in which it is transmitted;

receiving (106), from a wireless device (20), one or more measurements based on the one or more DRS signals transmitted using the at least two different transmission beams in the at least two different time resources; and

correlating (106) each of the one or more measurements with a respective beam of the at least two different transmit beams.

2. The method of claim 1 wherein transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises:

transmitting (200) the one or more DRS signals using a first transmission beam but not a second transmission beam in a first time resource; and

transmitting (202) the one or more DRS signals using the second transmission beam but not the first transmission beam in a second time resource, the second transmission beam being different from the first transmission beam, and the second time resource being different from the first time resource.

3. The method of claim 1 or 2, wherein the one or more DRS signals comprise channel state information reference signals, CSI-RS.

4. The method of claim 3, wherein the one or more DRS signals comprise:

primary synchronization signal PSS for physical cell identity PCI;

secondary synchronization signal SSS for the same PCI; and

common reference signal CRS for the same PCI.

5. The method according to any of claims 1 to 4, wherein each of the at least two different time resources is one of the group consisting of a slot, a subframe, a symbol time, a frame, a transmission time interval, TTI, and an interleaving time.

6. The method of any of claims 1-4 wherein the at least two different time resources are at least two different DRS occasions, and transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different DRS occasions.

7. The method of any of claims 1-4 wherein the at least two different time resources are at least two time resources within a same DRS occasion and transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources within the same DRS time.

8. The method of any of claims 1-7, wherein transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting (102) the same one or more DRS signals according to a DRS transmission beam pattern, the DRS transmission beam pattern defining the at least two different transmission beams of the at least two different time resources in which the one or more DRS signals are to be transmitted.

9. The method of claim 8 wherein the DRS transmit beam pattern is a symmetric DRS transmit beam pattern.

10. The method of claim 8 wherein the DRS transmit beam pattern is an asymmetric DRS transmit beam pattern.

11. The method of claim 8 wherein the DRS transmission beam pattern is an aperiodic DRS transmission beam pattern.

12. The method of any of claims 1-11, wherein transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises:

deciding (102A) to transmit the one or more DRS signals using a DRS transmit beam pattern;

deciding (102B) which DRS transmission beam pattern is to be used for transmitting the one or more DRS signals; and

transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources in accordance with the DRS transmission beam pattern.

13. The method of claim 12 wherein deciding (102A) to transmit the one or more DRS signals using a DRS transmit beam pattern comprises: determining (102A) to transmit the one or more DRS signals using a DRS transmit beam pattern based on one or more criteria selected from the group consisting of:

a criterion to receive a request to transmit a beam pattern using DRS from another network node (12, 16);

criteria for transmitting a beam pattern using DRS when beamforming is used or expected to be used by the transmission point (22);

criteria for using a DRS transmit beam pattern when the number of transmit beams being used or expected to be used by the transmit point (22) is greater than a predefined threshold;

criterion to transmit a beam pattern using DRS when there are a large number of radio nodes in a coverage area of the transmission point (22);

criteria to use the DRS to transmit a beam pattern when there are a limited number of different DRS resources available;

criteria for a DRS to transmit a beam pattern to be used for a particular deployment scenario;

a criterion to use the DRS to transmit a beam pattern when the system load is greater than a predefined threshold;

criteria based on measurement performance; and

a criterion to transmit a parameter based on one or more DRSs.

14. The method of any of claims 1-13, wherein transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting (102) the same one or more DRS signals in accordance with a DRS transmission beam pattern, the DRS transmission beam pattern defining the at least two different transmission beams of the at least two different time resources in which the one or more DRS signals are to be transmitted, and the method further comprising:

providing (104), to a wireless device (20), information related to transmission of the one or more DRS signals in the DRS transmission beam pattern.

15. The method of claim 14 wherein the information comprises an indication that the transmission point (22) is to or is expected to transmit DRS signals according to a DRS transmission beam pattern.

16. The method of claim 14 wherein the information includes an indication that the transmission point (22) is to or is expected to transmit the one or more DRS signals according to the DRS transmission beam pattern.

17. The method of claim 14 wherein the information comprises information related to transmitting DRS signals in a DRS transmission beam pattern in a plurality of cells (14, 18).

18. The method of any of claims 1-13, wherein transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting (102) the same one or more DRS signals in accordance with a DRS transmission beam pattern, the DRS transmission beam pattern defining the at least two different transmission beams of the at least two different time resources in which the one or more DRS signals are to be transmitted, and the method further comprising:

providing (104), to another network node (12,16), information related to transmission of the one or more DRS signals by the transmission point (22) in the DRS transmission beam pattern.

19. The method of claim 1, wherein:

transmitting (102) the same one or more DRS signals using the at least two different transmission beams in the at least two different time resources comprises: transmitting (102) the same one or more DRS signals according to a DRS transmission beam pattern, the DRS transmission beam pattern defining the at least two different transmission beams of the at least two different time resources in which the one or more DRS signals are to be transmitted; and

correlating (106) each of the one or more measurements with the respective one of the at least two different transmit beams comprises: correlating (106) each of the one or more measurements with the respective one of the at least two different transmit beams based on the known time resources in which the measurements were obtained and the DRS transmit beam pattern.

20. A transmission point (22) for a cellular communication network (10), comprising:

a transceiver (46);

a processor (42); and

a memory (44) storing instructions executable by the processor (42), whereby the transmission point (22) is operable to:

transmitting the same one or more discovery reference signals, DRS, signals via the transceiver (46) using at least two different transmission beams in at least two different time resources, each transmission beam being characterized by a direction in which it is transmitted;

receive, from a wireless device (20), one or more measurements based on the one or more DRS signals transmitted using the at least two different transmission beams in the at least two different time resources; and

correlating each of the one or more measurements with a respective beam of the at least two different transmit beams.

21. A transmission point (22) for a cellular communication network (10) adapted to:

transmitting the same one or more discovery reference signals, DRS, signals using at least two different transmission beams in at least two different time resources, each transmission beam being characterized by a direction in which it is transmitted;

22. The transmission point (22) of claim 21, wherein the transmission point (22) is further adapted to operate according to the method of any one of claims 2 to 19.

23. A transmission point (22) for a cellular communication network (10), comprising:

a discovery reference signal, DRS, transmission module (70) operable to transmit the same one or more DRS signals using at least two different transmission beams in at least two different time resources, each transmission beam being characterized by a direction in which it is transmitted; and

a measurement reception and usage module (72) operable to: receive, from a wireless device (20), one or more measurements based on the one or more DRS signals transmitted using the at least two different transmission beams in the at least two different time resources, and correlate each of the one or more measurements with a respective beam of the at least two different transmission beams.

24. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 1-19.

25. A carrier containing the computer program of claim 24, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

26. A non-transitory computer readable medium storing software instructions that, when executed by a processor (42) for a transmission point (22) of a cellular communication network (10), cause the transmission point (22) to: